do not rewrite <-> and -> for Spin LTL output

Fixes #39, reported by Joachim Klein.

* src/ltlvisit/lunabbrev.hh, src/ltlvisit/lunabbrev.cc: Take an option
to specify which of xor/equiv/implies should be rewritten.
* src/ltlvisit/print.cc (print_spin): Rewrite only xor.
* src/tests/ltlfilt.test: Add a test case.
* NEWS: Mention this.

NEWS

@@ -26,6 +26,8 @@ New in spot 1.99.2a (not yet released)
       double quotes where not always properly rendered.
     - A spurious assertion was triggered by streett_to_generalized_buchi(),
       but only when compiled in DEBUG mode.
+    - LTL formula rewritten in Spin's syntax no longer have their ->
+      and <-> rewritten aways.
 
 New in spot 1.99.2 (2015-07-18)
 

src/ltlvisit/lunabbrev.cc

@@ -1,6 +1,6 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2009, 2010, 2012, 2014 Laboratoire de Recherche et
+// Copyright (C) 2009, 2010, 2012, 2014, 2015 Laboratoire de Recherche
-// Développement de l'Epita (LRDE).
+// et Développement de l'Epita (LRDE).
 // Copyright (C) 2003, 2004 Laboratoire d'Informatique de Paris 6 (LIP6),
 // département Systèmes Répartis Coopératifs (SRC), Université Pierre
 // et Marie Curie.
@@ -29,8 +29,25 @@ namespace spot
   namespace ltl
   {
 
-    unabbreviate_logic_visitor::unabbreviate_logic_visitor()
+    unabbreviate_logic_visitor::unabbreviate_logic_visitor(const char* opt)
     {
+      while (*opt)
+	switch (char c = *opt++)
+	  {
+	  case '^':
+	    rewrite_xor = true;
+	    break;
+	  case 'i':
+	    rewrite_i = true;
+	    break;
+	  case 'e':
+	    rewrite_e = true;
+	    break;
+	  default:
+	    throw std::runtime_error
+	      (std::string("unknown option for unabbreviate_logic_visitor(): ")
+	       + c);
+	  }
     }
 
     unabbreviate_logic_visitor::~unabbreviate_logic_visitor()
@@ -42,29 +59,44 @@ namespace spot
     {
       const formula* f1 = recurse(bo->first());
       const formula* f2 = recurse(bo->second());
-
       binop::type op = bo->op();
       switch (op)
 	{
+	  /* f1 ^ f2  ==  !(f1 <-> f2) */
 	  /* f1 ^ f2  ==  (f1 & !f2) | (f2 & !f1) */
 	case binop::Xor:
 	  {
-	    const formula* a =
+	    if (!rewrite_xor)
-	      multop::instance(multop::And, f1->clone(),
+	      goto no_rewrite;
-			       unop::instance(unop::Not, f2->clone()));
+	    if (!rewrite_e)
-	    const formula* b =
+	      {
-	      multop::instance(multop::And, f2,
+		result_ = unop::instance(unop::Not,
-			       unop::instance(unop::Not, f1));
+					 binop::instance(binop::Equiv, f1, f2));
-	    result_ = multop::instance(multop::Or, a, b);
+		return;
-	    return;
+	      }
+	    else
+	      {
+		const formula* a =
+		  multop::instance(multop::And, f1->clone(),
+				   unop::instance(unop::Not, f2->clone()));
+		const formula* b =
+		  multop::instance(multop::And, f2,
+				   unop::instance(unop::Not, f1));
+		result_ = multop::instance(multop::Or, a, b);
+		return;
+	      }
 	  }
 	  /* f1 => f2  ==  !f1 | f2 */
 	case binop::Implies:
+	  if (!rewrite_i)
+	    goto no_rewrite;
 	  result_ = multop::instance(multop::Or,
 				     unop::instance(unop::Not, f1), f2);
 	  return;
 	  /* f1 <=> f2  ==  (f1 & f2) | (!f1 & !f2) */
 	case binop::Equiv:
+	  if (!rewrite_e)
+	    goto no_rewrite;
 	  {
 	    const formula* f1c = f1->clone();
 	    const formula* f2c = f2->clone();
@@ -90,6 +122,7 @@ namespace spot
 	case binop::UConcat:
 	case binop::EConcat:
 	case binop::EConcatMarked:
+	  no_rewrite:
 	  result_ = binop::instance(op, f1, f2);
 	  return;
 	}
@@ -99,15 +132,16 @@ namespace spot
     const formula*
     unabbreviate_logic_visitor::recurse(const formula* f)
     {
-      return unabbreviate_logic(f);
+      f->accept(*this);
+      return result_;
     }
 
     const formula*
-    unabbreviate_logic(const formula* f)
+    unabbreviate_logic(const formula* f, const char* xie)
     {
       if (f->is_sugar_free_boolean())
 	return f->clone();
-      unabbreviate_logic_visitor v;
+      unabbreviate_logic_visitor v(xie);
       f->accept(v);
       return v.result();
     }

src/ltlvisit/lunabbrev.hh

@@ -1,5 +1,5 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2012, 2013 Laboratoire de Recherche et Développement
+// Copyright (C) 2012, 2013, 2015 Laboratoire de Recherche et Développement
 // de l'Epita (LRDE).
 // Copyright (C) 2003, 2004  Laboratoire d'Informatique de Paris 6 (LIP6),
 // département Systèmes Répartis Coopératifs (SRC), Université Pierre
@@ -44,13 +44,17 @@ namespace spot
     {
       typedef clone_visitor super;
     public:
-      unabbreviate_logic_visitor();
+      unabbreviate_logic_visitor(const char* opt = "^ie");
       virtual ~unabbreviate_logic_visitor();
 
       using super::visit;
       void visit(const binop* bo);
 
       virtual const formula* recurse(const formula* f);
+    private:
+      bool rewrite_xor = false;
+      bool rewrite_i = false;
+      bool rewrite_e = false;
     };
 
     /// \ingroup ltl_rewriting
@@ -60,7 +64,12 @@ namespace spot
     /// This will rewrite binary operators such as binop::Implies,
     /// binop::Equals, and binop::Xor, using only unop::Not, multop::Or,
     /// and multop::And.
-    SPOT_API const formula* unabbreviate_logic(const formula* f);
+    ///
+    /// The optional \a opt argument can be a string containing any
+    /// subset of the string "^ie" to denote the operators (xor,
+    /// implication, equivalence) to actually remove.
+    SPOT_API const formula* unabbreviate_logic(const formula* f,
+					       const char* opt = "^ie");
 
   }
 }

src/ltlvisit/print.cc

@@ -121,8 +121,8 @@ namespace spot
 	"true",  // 1 doesn't work from the command line
 	"[*0]",			// not supported
 	" xor ",		// rewritten
-	" -> ",			// rewritten, although supported
+	" -> ",
-	" <-> ",		// rewritten, although supported
+	" <-> ",
 	" U ",
 	" V ",
 	" W ",			// rewritten
@@ -985,8 +985,8 @@ namespace spot
     std::ostream&
     print_spin_ltl(std::ostream& os, const formula* f, bool full_parent)
     {
-      // Remove xor, ->, and <-> first.
+      // Rewrite xor.
-      const formula* fu = unabbreviate_logic(f);
+      const formula* fu = unabbreviate_logic(f, "^");
       // Also remove W and M.
       f = unabbreviate_wm(fu);
       fu->destroy();

src/tests/ltlfilt.test

@@ -50,7 +50,6 @@ G(a & Xb)
 Xa
 F(a & !Xa & Xb)
 {a & {b|c} }
-
 EOF
 
 checkopt --eventual <<EOF
@@ -161,6 +160,7 @@ b & GF(a | c) & FG(a | c)
 G(d & e) | FG(Xf| !c) | h | i
 b & !Xc & e & (f | g)
 b & GF(a | c) & !GF!(a | c)
+F(a <-> b) -> (c xor d)
 EOF
 
 cat >exp <<EOF
@@ -168,6 +168,7 @@ p0 & Xp1
 p0 & p1 & GF(p0 | p2) & FG(p0 | p2)
 p0 & GFp1 & FGp1
 p0 | Gp1 | FG(p2 | Xp3)
+p0 | Gp1
 EOF
 
 run 0 $ltlfilt -u --nnf --relabel-bool=pnn in >out
@@ -189,11 +190,55 @@ p0 && []<>p1 && <>[]p1
 #define p2 (!c)
 #define p3 (f)
 p0 || []p1 || <>[](p2 || Xp3)
+#define p0 ((c && !d) || (!c && d))
+#define p1 ((a && !b) || (!a && b))
+p0 || []p1
 EOF
 
 run 0 $ltlfilt -s -u --nnf --relabel-bool=pnn --define in >out
 diff exp out
 
+cat >exp <<EOF
+#define p0 (a)
+#define p1 (c)
+#define p2 (b)
+p0 && p1 && Xp2
+#define p0 (a)
+#define p1 (b)
+#define p2 (c)
+p0 && p1 && []<>(p0 || p2) && <>[](p0 || p2)
+#define p0 (b)
+#define p1 (a)
+#define p2 (c)
+p0 && []<>(p1 || p2) && <>[](p1 || p2)
+#define p0 (h)
+#define p1 (i)
+#define p2 (d)
+#define p3 (e)
+#define p4 (c)
+#define p5 (f)
+p0 || p1 || [](p2 && p3) || <>[](!p4 || Xp5)
+#define p0 (b)
+#define p1 (e)
+#define p2 (f)
+#define p3 (g)
+#define p4 (c)
+p0 && p1 && (p2 || p3) && !Xp4
+#define p0 (b)
+#define p1 (a)
+#define p2 (c)
+p0 && []<>(p1 || p2) && ![]<>!(p1 || p2)
+#define p0 (a)
+#define p1 (b)
+#define p2 (c)
+#define p3 (d)
+<>(p0 <-> p1) -> !(p2 <-> p3)
+EOF
+
+run 0 $ltlfilt -s -u --relabel=pnn --define in >out
+diff exp out
+
+toolong='((p2=0) * (p3=1))' # work around the 80-col check
 cat >exp <<EOF
 #define p0 ((a=1))
 #define p1 ((c=1))
@@ -220,6 +265,11 @@ cat >exp <<EOF
 #define p3 ((g=1))
 #define p4 ((c=1))
 (p0=1) * (p1=1) * ((p2=1) + (p3=1)) * (X(p4=0))
+#define p0 ((c=1))
+#define p1 ((d=1))
+#define p2 ((a=1))
+#define p3 ((b=1))
+((p0=1) * (p1=0)) + ((p0=0) * (p1=1)) + (G(((p2=1) * (p3=0)) + $toolong))
 EOF
 run 0 $ltlfilt -p --wring -u --nnf --relabel=pnn --define in >out
 diff exp out
@@ -233,6 +283,7 @@ b & GF(a | c) & FG(a | c)@
 h | i | G(d & e) | FG(!c | Xf)@
 b & e & (f | g) & !Xc@
 b & GF(a | c) & !GF!(a | c)@
+F(a <-> b) -> (c xor d)@
 EOF
 diff exp out